When a user executes an input operation for adjusting the volume, selecting a song, or the like on a small portable electronic device such as a portable music player, the user needs to extract the device from a pocket, a bag, or the like storing the device. As a technique to avoid this action, Patent Literature 1 describes a mobile phone device. According to Patent Literature 1, some of the mobile phone functions are attached to a portion on an arm of the user.
In addition, Patent Literature 2 discloses a phone device that is attached to a portion on an ear of the user and that realizes phone functions based on trigger signals generated when teeth of the user are clicked.
In addition, Patent Literature 3 describes an input device configured in the shape of a wristwatch. The input device receives gestures, such as gripping, releasing, twisting, and shaking, as commands.
Patent Literature 1:
Japanese Patent Kokai Publication No. JP-H10-051527A
Patent Literature 2:
Japanese Patent Kokai Publication No. JP-H10-200610A
Patent Literature 3:
Japanese Patent Kokai Publication No. JP2002-358149A